1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer, etc., and more particularly to an image forming apparatus having a revolving type developing apparatus rotatably supported in the image forming apparatus.
2. Discussion of the Background
An image forming apparatus is known which includes a revolving type developing apparatus with a plurality of developing units having developing devices around a rotary shaft. The developing devices are rotated by rotation of the rotary shaft so as to move an arbitrary developing device to a developing station adjacent to a latent image carrier in order to develop the latent image formed on the latent image carrier by the developing device. A revolving type developing apparatus is also known which includes a rotary developing unit rotatably arranged close to a photo-conductive drum as a latent image carrier having a plurality of developing devices. In such a device, a rotary toner container unit having a plurality of toner containers corresponding one-to-one to the plurality of developing devices is arranged coaxially on one end of the rotary developing unit, and a toner conveying device connects each toner container and each developing device as shown in, for example, Japanese Non-examined Patent Publication No. 62-251772, Japanese Non-examined Patent Publication No. 63-78170, and Japanese Non-examined Patent Publication No. 63-41164.
In the above Japanese Non-examined Patent Publication No. 63-78170, a rotary developing unit supporting mechanism is disclosed for rotatably supporting a wall of one end of both end portions of a developing unit in a direction of a rotary shaft with a rotatable supporting roller which is in contact with its circumferential surface in order to support the rotary developing unit in the apparatus and for rotatably supporting the other end wall on a pin fixed to a center of it in a positioning hole on a side plate.
In addition, in order to enhance workability of maintenance such as exchanging developer in a developing device, an image forming apparatus is disclosed to have a constitution in which a photo-conductive drum as a latent image carrier and working devices such as a normal developing apparatus are supported by a unit supporter which is held to be pulled out of a body of the image forming apparatus (hereinafter, simply referred to as an apparatus body). Such a technology is shown in, for example, Japanese Patent Publication No. 61-58035, Japanese Patent Publication No. 62-37392, Japanese Patent Publication No. 3-34070, Japanese Patent Publication No. 58-54392 and Japanese Patent Publication No. 3-50268, etc.
One drawback in such background devices is that a revolving type developing apparatus, however, is grasped by an apparatus body for fixing in order to assure its rigidity and precision, which leads to extremely deteriorated maintainability around the developing unit. Furthermore, in an image forming apparatus having this constitution, the revolving type developing apparatus and the apparatus body cannot be individually assembled due to the grasped fixing method of the revolving type developing apparatus to be fixed to the apparatus body, which causes a serious problem in assembly properties in a mass production line.
Although there is also an image forming apparatus in which only a revolving type developing apparatus is removable from an apparatus body, in this type of image forming apparatus a number of components of the revolving type developing apparatus is increased, which expands a tolerance generated by building-up of the components from a stage of its photo-conductive drum to the revolving type developing apparatus, and therefore it becomes hard to assure a precision of a developing gap between a developing roller of a developing device in a developing unit of the revolving type developing apparatus and the photoconductive drum, and as a result a stable image quality cannot be obtained. In addition, in this constitution, the revolving type developing apparatus removed from the apparatus body is put on a floor before its maintenance work is started, which deteriorates stability and workability of the revolving type developing apparatus during the work, since the revolving type developing apparatus is a rotary body and the revolving type developing apparatus is attached or removed to or from the apparatus body in side directions which forces a user to work in an unnatural posture with poor workability.
As a further drawback in the image forming apparatus having the above unit support structure, various problems are generated when freely rotating the revolving type developing apparatus as the revolving type developing apparatus supported by the unit supporter.
For example, if a user pulls out the revolving type developing apparatus supported by the unit supporter and then tries to start a maintenance work such as mounting or removing each developing device in the rotary developing unit in this state, the revolving type developing apparatus freely rotates since it is separated from a driving input in the side of the apparatus body. This causes a problem in that it is hard to perform the maintenance work, which thereby deteriorates working efficiency.
Furthermore, if the revolving type developing apparatus rocks due to vibrations during transportation with the unit support housed in the apparatus body, the following problems may arise. For example, if the image forming apparatus has a drive transmission mechanism which drives a rotary member, such as, for example, a developing roller in the revolving type developing apparatus, by means of mating gears between the apparatus body and the revolving type developing apparatus and it is transported with the gears mated to each other, the revolving type developing apparatus rocks around a rotary shaft due to vibrations during the transportation. This may cause rotations in forward and reverse directions of members for stirring and conveying developer in each developing device of the revolving type developing apparatus and of the developing roller, and as a result toner may leak outside through a gap between an opening edge for an exposure of the developing roller in a developing device case and a surface of the developing roller (if 2-component developer is used, carrier and toner may leak) or the toner may scatter.
In addition, if the revolving type developing apparatus has a rotary toner container device and the apparatus body is transported with toner contained in each toner container of the rotary toner container device, the toner in each toner container may flow out and move into each developing device via the toner conveying device. The toner may then leak outside through the gap between the opening edge for the exposure of the developing roller in the developing device case and the surface of the developing roller, or the toner may scatter.